Survival Behavior Of Escherichia Coli O157:H7 In Soil From Areas With Different Land Use Types

E.coli O157:H7 is highly pathogenic food-borne pathogenwith a low-infection dose.The typical symptomsinclude hemorrhagic diarrhea and enteritis,hemolytic uremic syndrome,thrombotic thrombocytopenic purpura,and might cause deaths.E.coli O157:H7 was firstly isolated in 1982,it has caused many outbreaks later and constitutes a serious public health issue.In agricultural farmland,farmersapply E.coli O157:H7containing manure or irrigation water to the soils,thus contaminate thefruits and vegetables.The feces carrying E.coliO157:H7 will also contaminate the soil in nomadic areas and make it also pose a majorthreat to public health.Therefore,it is of greatimportance to understand the survival behavior and its influencing factors of E.coli O157:H7in the soil environment.This thesismonitored the growth curve of E.coli O157:H7 at 37°C and screened the rifampicin and naldixic acid resistancestrains using induced spontaneous mutagenesis protocol.We collected the soil samples from areas of three different land-use types in northeastern China.A total of 24 soil samples were collected from agro-pastoralsoil(TL1?8),the vegetable-growing soil(SP1?8),and apple pearsoil(YJ1?8).Dynamic survivalof E.coli O157:H7 in a soil sample was monitored.The survival behaviorof E.coli O157:H7 in soils was comprehensively discussed.The intrinsic relationship between the survival behaviors of E.coli O157:H7 in soils and soil properties was discussed.The main findings are as follows:(1)The average survival time of E.coli O157:H7 in soils of three different land use types: agro-pastoralarea(38.75 days)<fruit area(67.09 days)<vegetable garden(68.27 days),in Weibull model,? is significantly correlated with ttd(P<0.05),indicating that ? may be a better biological indicator of E.coli O157:H7 persistence in agricultural soil.(2)According to multiple linear regression analysis and PCA analysis,it can be concluded that the survival time(ttd)of E.coli O157:H7 is related to the soil clay content,total nitrogen,and soil salinity.The survival time(ttd)showed positive correlation withclay content(P<0.001),a negative correlation with total nitrogen and salinity ofthe soil(P<0.05).Insoils from the agro-pastoral zone,the factor affecting the survival of E.coli O157:H7 is ammonium nitrogen;in the vegetable-growing soils,the soil property affecting the survival of E.coliO157:H7 is total nitrogen.In the soilsfrom apple pear garden,the soilproperty affecting the survival of E.coli O157:H7 is nitrate-nitrogen.Thesoil microbial diversity indices had no significant correlation with the survival time of E.coli O157:H7.(3)According to the VPA analysis,the bacteria,fungi,and physicochemical properties in the soil have someinfluence on the survival time of E.coli O157:H7,which bacteria is particularly prominent,accounting for 58.3% of the overall variation of the survival time;The data from the study showed that the fungihad little effect on the survival of E.coli O157:H7,accounting for 1.0%of overall variation of survival time.